I’ve noticed that if one of them has flu and has the cure of flu as a wish, then even if a doctor successfully treats the flu the wish is not fulfilled, meaning that wish can effectively not be fulfilled unless by using points unnecessarily.

Hey Yuhg. When the treatment is successful, the flu doesn’t disappear immediately but goes from from stage 4 to stage 3 for example.
The wish only disappears when the flu is fully healed, could that be what you’re observing?